Slide-valve



(NO Model.)

'1 DE GRAPE;

SLIDE VALVE.

Patented Apr. 29

N. FFTERS. Ptmta-uthn hm Wnhlngbn. 0.6.

UNITED STATES PATENT I OFFICE.

ISAAC DE GRAFF, OF DETROIT, MICHIGAN.

SLI DE-VALVE.

SPECIFICATION forming part of Letters Patent No. 297,682, dated April 29, 1884.

Application filed October 1, 1883. (No model.)

To all whom it may concern:

Be it known that I, ISAAC DE GRAFF, of Detroit, in the county of WVayne and State of Michigan, 'have invented new and useful Improvements in Slide-Valves; and I do hereby declare that the following is a full, clear, and

exact description thereof, reference being bad to the accompanying drawings, which form part of this specification- This invention relates to certain new and useful improvements in the construction of ment of the parts, all as more fully hereinafinto the exhaust-passage d.

slide-valves, the object beingto obtain the maximum of openings for both steam and exhaust with a minimum travel, valve-area,and clearance.

To this end the invention consists in the peculiar relative construction and arrangeter set forth.

In the accompanying drawings, which form a part of this specification, Figure 1 shows my improved valve in vertical longitudinal section, in which A represents the'valve-case, B the cylinder to which it is connected, and O the valve. Fig. 2 is an end section of the same on the line 0 D of Fig. 1. Y

Certain proportions in all valves are arbitrary-such as thelap, travel, and bridges. Having assumed that the ports a aim the cylinder and a in the valve equal seven-sixteenths, the bridges b b iive-eighths, and the bridge 0 of the valve equal to the port a, and the exhaust-lap one-sixteenth, the exhaust- I port (2 must equal the bridge 0 and twice the 35 steam-ports, while-the port 6 of the valve must equal the bridge I) and twice one of the ports a; the bridge f must be equal to the width of the port a plus the steam and exhaust lap.

having thus decided the relative propor: tions, the operation is as follows: The valve being in mid-position and moved by the eccentric in the direction of the arrow, the first function performed by the valve is to open the exhaust-port at g, as in the ordinary valves; but at the same time an opening is made from the cylinder through the port a, at h h widens to the same extent as does the opening at g, and remains open for the same period.

This opening from the steam-space in the chest into the,

steam-port a, as at It, from beneath the valve, the passage 0. being in this case a live-steam port, this operation of the parts being reversed on the return-stroke; and I obtain by this arrangement twice the usual port-openings for a' given amount of travel.

I attach importance to the bridge I), the offices of which are, first, to regulate the exhaust-lead; second, to reduce the clearance in the main steam-port; third, to give direction to the current of steam to and from the cylinder and through the valve, and, fourth, to afford an additional support to the valve in its passage over the port a.

It is obvious'that any proportion of lead, lap, steamportsand bridges other than those given may be taken, so long asthe relative proportions herein given are preserved.

I am aware of Patents Nos. 35,068 and 95,868, and make no claim to anything shown therein as forming part of my invention.

What I claim as my invention is- 1. A Q-valve provided with a passage, a, and a passage, e, with the bridge a between them, serving to close theexhaustport when the live steam is passing through the passage a, and both passages being contained wholly within said va1ve,and terminating in exhaustsagesa and e, and the ports a and d of the cylinder, and the latter having the bridge I), and allrelatively proportioned to the lap, travel, and bridges, substantially asset forth.

\ ISAAC GRAFF.

Witnesses:

' H. S. SPRAGUE,

E. W. ANDREWS. 

